I've known for a while that I waste far too much time on reading RSS feeds. The worst time-sink was the New York Times, in particular, the popular articles and the headlines. As one of my friends noted, the New York Times has been leaning more and more towards soft news because unfortunately, that is what sells. People don't really care what's happening in Iraq. They'd rather read about autism or college admissions. Anyone who actually cares about world news will flip to the relevant section anyways.
So now my news feeds consist of the New York Times national news, New York Times international news, Wall Street Journal US business news, Wall Street Journal economy news, and Wall Street Journal market news sections.
In addition, my daily blog reading includes the headlines of physics articles, a physics blog or two, the Chronicle of Higher Education, Lifehacker, the Writer's Almanac, and a photo or two. I think this gives me the most efficient and representative mix of work, news, and culture.